What are pipe threads

Pipe Threads

When we talk about pipe fittings, it means that fittings are used to connect two or more pipes in two ways—either by threads or by slip fit. While metal pipes are threaded, the plastic pipe can be threaded or slip fit. A threaded pipe has screw-threaded ends for assembly or they screw together to connect.

For pipe thread sizes, “½–14 NPT” identifies a pipe thread with a nominal inside diameter of ½ inch and 14 threads to the inch and these threads are made according to the NPT standard. The pipe has a left hand thread if “LH” is added. The pipe thread standards followed in US are:

The word “taper” mentioned above refers to the difference between many pipe threads and those on bolts and screws. Pipe threads not only a make mechanical joint but also a leak proof one. To do this, the threads become shallower the farther they are from the end of the fitting or the pipe. The bottoms of the threads taper. The taper is 1/16 inch in an inch.

Because of the taper, a pipe can only screw into a pipe fitting a little distance before it jams. The standard represents this distance, the effective thread. The standard also represents another distance, the engagement, which is the distance the pipe can be screwed in by hand, without much effort. For workers, it is more easy to know how many turns to make by hand or with a wrench.

Types of threads:Various threads available in pipe and pipe fittings are as follows:

Right-handed or Left-handed ThreadsNearly all threads are oriented so that a bolt or nut or any fitting can be tightened. By turning it in a clockwise direction, the item turned moves away from the viewer. And it is loosened by turning anticlockwise when the item moves towards the viewer . This is known as a right-handed thread. Left-handed threads are oriented in the opposite direction. There are also self-tapping screw threads where no nut or bolt is required.

Male ThreadsIn male threads, the threads of the pipe are on the outside. Here, tapered pipe threads like NPT, BSPT etc. are used sealing without gaskets.

Female ThreadsIn female threads, the threads are on the inside. Here too, like male threads, tapered pipe threads are used for sealing.